Dynamics of circulating tumor DNA during postoperative radiotherapy in patients with residual triple-negative breast cancer following neoadjuvant chemotherapy: a prospective observational study.
This study was performed to evaluate circulating tumor DNA (ctDNA) kinetics during postoperative radiotherapy (PORT) in patients with residual triple-negative breast cancer (TNBC) at surgery following neoadjuvant chemotherapy (NAC).
Stage II/III patients with post-NAC residual TNBC who required PORT were prospectively included in this study between March 2019 and July 2020. For 11 TNBC patients, next-generation sequencing targeting 38 genes was conducted in 55 samples, including tumor tissue, three plasma samples, and leukocytes from each patient. The plasma samples were collected at three-time points; pre-PORT (T0), after 3 weeks of PORT (T1), and 1 month after PORT (T2). Serial changes in ctDNA variant allele frequency (VAF) were analyzed.
Somatic variants were found in the tumor specimens in 9 out of 11 (81.8%) patients. Mutated genes included TP53 (n = 7); PIK3CA (n = 2); and AKT1, APC, CSMD3, MYC, PTEN, and RB1 (n = 1). These tumor mutations were not found in plasma samples. Plasma ctDNA variants were detected in three (27.3%) patients at T0. Mutations in EGFR (n = 1), CTNNB1 (n = 1), and MAP2K (n = 1) was identified with ctDNA analysis. In two (18.2%) patients, the ctDNA VAF decreased through T1 and T2 while increasing at T2 in one (9.1%) patient. After a median follow-up of 22 months, no patient showed cancer recurrence.
Among patients with post-NAC residual TNBC, more than a quarter exhibited a detectable amount of ctDNA after curative surgery. The ctDNA VAF changed variably during the course of PORT. Therefore, ctDNA kinetics can serve as a biomarker for optimizing adjuvant treatment.
Publication Date: 2021-06-22
Journal: Breast cancer research and treatment
Clinical significance of TP53 variants as possible secondary findings in tumor-only next-generation sequencing.
In tumor-only next-generation sequencing (NGS), identified variants have the potential to be secondary findings (SFs), but they require verification through additional germline testing. In the present study, 194 patients with advanced cancer who underwent tumor-only NGS between April 2015 and March 2018 were enrolled, and the incidences of possible and true SFs were evaluated. Among them, 120 patients (61.9%) harbored at least one possible SF. TP53 was the most frequent gene in which 97 variants were found in 91 patients (49.5%). Nine patients provided informed consent to undergo additional germline testing, and a total of 14 variants (BRCA1, n = 1; BRCA2, n = 2; PTEN, n = 2; RB1, n = 1; SMAD4, n = 1; STK11, n = 1; TP53, n = 6) were analyzed. Three variants (BRCA1, n = 1; BRCA2, n = 2) were confirmed to be SFs, whereas TP53 variants were confirmed to be somatic variants. To confirm the low prevalence of SFs in TP53, we analyzed 24 patients with TP53 variants who underwent a paired tumor-normal NGS assay. As expected, all TP53 variants were confirmed to be somatic variants. A total of 30 patients were tested for germline variants in TP53, but none of them resulted in true SFs, suggesting the low prevalence of SFs in this gene. Therefore, the significance of additional germline testing for TP53 variants appears to be relatively low in daily clinical practice using a tumor-only NGS assay, unless patients have any relevant medical or family history.
Publication Date: 2019-10-20
Journal: Journal of human genetics